/* $NetBSD: mux.c,v 1.23.2.1 2023/12/25 12:31:05 martin Exp $ */ /* $OpenBSD: mux.c,v 1.101 2023/11/23 03:37:05 dtucker Exp $ */ /* * Copyright (c) 2002-2008 Damien Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ /* ssh session multiplexing support */ #include "includes.h" __RCSID("$NetBSD: mux.c,v 1.23.2.1 2023/12/25 12:31:05 martin Exp $"); #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "atomicio.h" #include "xmalloc.h" #include "log.h" #include "ssh.h" #include "ssh2.h" #include "pathnames.h" #include "misc.h" #include "match.h" #include "sshbuf.h" #include "channels.h" #include "msg.h" #include "packet.h" #include "monitor_fdpass.h" #include "sshpty.h" #include "sshkey.h" #include "readconf.h" #include "clientloop.h" #include "ssherr.h" #include "misc.h" /* from ssh.c */ extern int tty_flag; extern Options options; extern char *host; extern struct sshbuf *command; extern volatile sig_atomic_t quit_pending; /* Context for session open confirmation callback */ struct mux_session_confirm_ctx { u_int want_tty; u_int want_subsys; u_int want_x_fwd; u_int want_agent_fwd; struct sshbuf *cmd; char *term; struct termios tio; char **env; u_int rid; }; /* Context for stdio fwd open confirmation callback */ struct mux_stdio_confirm_ctx { u_int rid; }; /* Context for global channel callback */ struct mux_channel_confirm_ctx { u_int cid; /* channel id */ u_int rid; /* request id */ int fid; /* forward id */ }; /* fd to control socket */ int muxserver_sock = -1; /* client request id */ u_int muxclient_request_id = 0; /* Multiplexing control command */ u_int muxclient_command = 0; /* Set when signalled. */ static volatile sig_atomic_t muxclient_terminate = 0; /* PID of multiplex server */ static u_int muxserver_pid = 0; static Channel *mux_listener_channel = NULL; struct mux_master_state { int hello_rcvd; }; /* mux protocol messages */ #define MUX_MSG_HELLO 0x00000001 #define MUX_C_NEW_SESSION 0x10000002 #define MUX_C_ALIVE_CHECK 0x10000004 #define MUX_C_TERMINATE 0x10000005 #define MUX_C_OPEN_FWD 0x10000006 #define MUX_C_CLOSE_FWD 0x10000007 #define MUX_C_NEW_STDIO_FWD 0x10000008 #define MUX_C_STOP_LISTENING 0x10000009 #define MUX_C_PROXY 0x1000000f #define MUX_S_OK 0x80000001 #define MUX_S_PERMISSION_DENIED 0x80000002 #define MUX_S_FAILURE 0x80000003 #define MUX_S_EXIT_MESSAGE 0x80000004 #define MUX_S_ALIVE 0x80000005 #define MUX_S_SESSION_OPENED 0x80000006 #define MUX_S_REMOTE_PORT 0x80000007 #define MUX_S_TTY_ALLOC_FAIL 0x80000008 #define MUX_S_PROXY 0x8000000f /* type codes for MUX_C_OPEN_FWD and MUX_C_CLOSE_FWD */ #define MUX_FWD_LOCAL 1 #define MUX_FWD_REMOTE 2 #define MUX_FWD_DYNAMIC 3 static void mux_session_confirm(struct ssh *, int, int, void *); static void mux_stdio_confirm(struct ssh *, int, int, void *); static int mux_master_process_hello(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_new_session(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_alive_check(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_terminate(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_open_fwd(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_close_fwd(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_stdio_fwd(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_stop_listening(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static int mux_master_process_proxy(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); static const struct { u_int type; int (*handler)(struct ssh *, u_int, Channel *, struct sshbuf *, struct sshbuf *); } mux_master_handlers[] = { { MUX_MSG_HELLO, mux_master_process_hello }, { MUX_C_NEW_SESSION, mux_master_process_new_session }, { MUX_C_ALIVE_CHECK, mux_master_process_alive_check }, { MUX_C_TERMINATE, mux_master_process_terminate }, { MUX_C_OPEN_FWD, mux_master_process_open_fwd }, { MUX_C_CLOSE_FWD, mux_master_process_close_fwd }, { MUX_C_NEW_STDIO_FWD, mux_master_process_stdio_fwd }, { MUX_C_STOP_LISTENING, mux_master_process_stop_listening }, { MUX_C_PROXY, mux_master_process_proxy }, { 0, NULL } }; /* Cleanup callback fired on closure of mux client _session_ channel */ static void mux_master_session_cleanup_cb(struct ssh *ssh, int cid, int force, void *unused) { Channel *cc, *c = channel_by_id(ssh, cid); debug3_f("entering for channel %d", cid); if (c == NULL) fatal_f("channel_by_id(%i) == NULL", cid); if (c->ctl_chan != -1) { if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL) fatal_f("channel %d missing control channel %d", c->self, c->ctl_chan); c->ctl_chan = -1; cc->remote_id = 0; cc->have_remote_id = 0; chan_rcvd_oclose(ssh, cc); } channel_cancel_cleanup(ssh, c->self); } /* Cleanup callback fired on closure of mux client _control_ channel */ static void mux_master_control_cleanup_cb(struct ssh *ssh, int cid, int force, void *unused) { Channel *sc, *c = channel_by_id(ssh, cid); debug3_f("entering for channel %d", cid); if (c == NULL) fatal_f("channel_by_id(%i) == NULL", cid); if (c->have_remote_id) { if ((sc = channel_by_id(ssh, c->remote_id)) == NULL) fatal_f("channel %d missing session channel %u", c->self, c->remote_id); c->remote_id = 0; c->have_remote_id = 0; sc->ctl_chan = -1; if (sc->type != SSH_CHANNEL_OPEN && sc->type != SSH_CHANNEL_OPENING) { debug2_f("channel %d: not open", sc->self); chan_mark_dead(ssh, sc); } else { if (sc->istate == CHAN_INPUT_OPEN) chan_read_failed(ssh, sc); if (sc->ostate == CHAN_OUTPUT_OPEN) chan_write_failed(ssh, sc); } } channel_cancel_cleanup(ssh, c->self); } /* Check mux client environment variables before passing them to mux master. */ static int env_permitted(const char *env) { u_int i; int ret; char name[1024], *cp; if ((cp = strchr(env, '=')) == NULL || cp == env) return 0; ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env); if (ret <= 0 || (size_t)ret >= sizeof(name)) { error_f("name '%.100s...' too long", env); return 0; } for (i = 0; i < options.num_send_env; i++) if (match_pattern(name, options.send_env[i])) return 1; return 0; } /* Mux master protocol message handlers */ static int mux_master_process_hello(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { u_int ver; struct mux_master_state *state = (struct mux_master_state *)c->mux_ctx; int r; if (state == NULL) fatal_f("channel %d: c->mux_ctx == NULL", c->self); if (state->hello_rcvd) { error_f("HELLO received twice"); return -1; } if ((r = sshbuf_get_u32(m, &ver)) != 0) { error_fr(r, "parse"); return -1; } if (ver != SSHMUX_VER) { error_f("unsupported multiplexing protocol version %u " "(expected %u)", ver, SSHMUX_VER); return -1; } debug2_f("channel %d client version %u", c->self, ver); /* No extensions are presently defined */ while (sshbuf_len(m) > 0) { char *name = NULL; size_t value_len = 0; if ((r = sshbuf_get_cstring(m, &name, NULL)) != 0 || (r = sshbuf_get_string_direct(m, NULL, &value_len)) != 0) { error_fr(r, "parse extension"); return -1; } debug2_f("Unrecognised extension \"%s\" length %zu", name, value_len); free(name); } state->hello_rcvd = 1; return 0; } /* Enqueue a "ok" response to the reply buffer */ static void reply_ok(struct sshbuf *reply, u_int rid) { int r; if ((r = sshbuf_put_u32(reply, MUX_S_OK)) != 0 || (r = sshbuf_put_u32(reply, rid)) != 0) fatal_fr(r, "reply"); } /* Enqueue an error response to the reply buffer */ static void reply_error(struct sshbuf *reply, u_int type, u_int rid, const char *msg) { int r; if ((r = sshbuf_put_u32(reply, type)) != 0 || (r = sshbuf_put_u32(reply, rid)) != 0 || (r = sshbuf_put_cstring(reply, msg)) != 0) fatal_fr(r, "reply"); } static int mux_master_process_new_session(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { Channel *nc; struct mux_session_confirm_ctx *cctx; char *cmd, *cp; u_int i, j, env_len, escape_char, window, packetmax; int r, new_fd[3]; /* Reply for SSHMUX_COMMAND_OPEN */ cctx = xcalloc(1, sizeof(*cctx)); cctx->term = NULL; cctx->rid = rid; cmd = NULL; cctx->env = NULL; env_len = 0; if ((r = sshbuf_skip_string(m)) != 0 || /* reserved */ (r = sshbuf_get_u32(m, &cctx->want_tty)) != 0 || (r = sshbuf_get_u32(m, &cctx->want_x_fwd)) != 0 || (r = sshbuf_get_u32(m, &cctx->want_agent_fwd)) != 0 || (r = sshbuf_get_u32(m, &cctx->want_subsys)) != 0 || (r = sshbuf_get_u32(m, &escape_char)) != 0 || (r = sshbuf_get_cstring(m, &cctx->term, NULL)) != 0 || (r = sshbuf_get_cstring(m, &cmd, NULL)) != 0) { malf: free(cmd); for (j = 0; j < env_len; j++) free(cctx->env[j]); free(cctx->env); free(cctx->term); free(cctx); error_f("malformed message"); return -1; } #define MUX_MAX_ENV_VARS 4096 while (sshbuf_len(m) > 0) { if ((r = sshbuf_get_cstring(m, &cp, NULL)) != 0) goto malf; if (!env_permitted(cp)) { free(cp); continue; } cctx->env = xreallocarray(cctx->env, env_len + 2, sizeof(*cctx->env)); cctx->env[env_len++] = cp; cctx->env[env_len] = NULL; if (env_len > MUX_MAX_ENV_VARS) { error_f(">%d environment variables received, " "ignoring additional", MUX_MAX_ENV_VARS); break; } } debug2_f("channel %d: request tty %d, X %d, agent %d, subsys %d, " "term \"%s\", cmd \"%s\", env %u", c->self, cctx->want_tty, cctx->want_x_fwd, cctx->want_agent_fwd, cctx->want_subsys, cctx->term, cmd, env_len); if ((cctx->cmd = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put(cctx->cmd, cmd, strlen(cmd))) != 0) fatal_fr(r, "sshbuf_put"); free(cmd); cmd = NULL; /* Gather fds from client */ for(i = 0; i < 3; i++) { if ((new_fd[i] = mm_receive_fd(c->sock)) == -1) { error_f("failed to receive fd %d from client", i); for (j = 0; j < i; j++) close(new_fd[j]); for (j = 0; j < env_len; j++) free(cctx->env[j]); free(cctx->env); free(cctx->term); sshbuf_free(cctx->cmd); free(cctx); reply_error(reply, MUX_S_FAILURE, rid, "did not receive file descriptors"); return -1; } } debug3_f("got fds stdin %d, stdout %d, stderr %d", new_fd[0], new_fd[1], new_fd[2]); /* XXX support multiple child sessions in future */ if (c->have_remote_id) { debug2_f("session already open"); reply_error(reply, MUX_S_FAILURE, rid, "Multiple sessions not supported"); cleanup: close(new_fd[0]); close(new_fd[1]); close(new_fd[2]); free(cctx->term); if (env_len != 0) { for (i = 0; i < env_len; i++) free(cctx->env[i]); free(cctx->env); } sshbuf_free(cctx->cmd); free(cctx); return 0; } if (options.control_master == SSHCTL_MASTER_ASK || options.control_master == SSHCTL_MASTER_AUTO_ASK) { if (!ask_permission("Allow shared connection to %s? ", host)) { debug2_f("session refused by user"); reply_error(reply, MUX_S_PERMISSION_DENIED, rid, "Permission denied"); goto cleanup; } } /* Try to pick up ttymodes from client before it goes raw */ if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1) error_f("tcgetattr: %s", strerror(errno)); window = CHAN_SES_WINDOW_DEFAULT; packetmax = CHAN_SES_PACKET_DEFAULT; if (cctx->want_tty) { window >>= 1; packetmax >>= 1; } nc = channel_new(ssh, "session", SSH_CHANNEL_OPENING, new_fd[0], new_fd[1], new_fd[2], window, packetmax, CHAN_EXTENDED_WRITE, "client-session", CHANNEL_NONBLOCK_STDIO); nc->ctl_chan = c->self; /* link session -> control channel */ c->remote_id = nc->self; /* link control -> session channel */ c->have_remote_id = 1; if (cctx->want_tty && escape_char != 0xffffffff) { channel_register_filter(ssh, nc->self, client_simple_escape_filter, NULL, client_filter_cleanup, client_new_escape_filter_ctx((int)escape_char)); } debug2_f("channel_new: %d linked to control channel %d", nc->self, nc->ctl_chan); channel_send_open(ssh, nc->self); channel_register_open_confirm(ssh, nc->self, mux_session_confirm, cctx); c->mux_pause = 1; /* stop handling messages until open_confirm done */ channel_register_cleanup(ssh, nc->self, mux_master_session_cleanup_cb, 1); /* reply is deferred, sent by mux_session_confirm */ return 0; } static int mux_master_process_alive_check(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { int r; debug2_f("channel %d: alive check", c->self); /* prepare reply */ if ((r = sshbuf_put_u32(reply, MUX_S_ALIVE)) != 0 || (r = sshbuf_put_u32(reply, rid)) != 0 || (r = sshbuf_put_u32(reply, (u_int)getpid())) != 0) fatal_fr(r, "reply"); return 0; } static int mux_master_process_terminate(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { debug2_f("channel %d: terminate request", c->self); if (options.control_master == SSHCTL_MASTER_ASK || options.control_master == SSHCTL_MASTER_AUTO_ASK) { if (!ask_permission("Terminate shared connection to %s? ", host)) { debug2_f("termination refused by user"); reply_error(reply, MUX_S_PERMISSION_DENIED, rid, "Permission denied"); return 0; } } quit_pending = 1; reply_ok(reply, rid); /* XXX exit happens too soon - message never makes it to client */ return 0; } static char * format_forward(u_int ftype, struct Forward *fwd) { char *ret; switch (ftype) { case MUX_FWD_LOCAL: xasprintf(&ret, "local forward %.200s:%d -> %.200s:%d", (fwd->listen_path != NULL) ? fwd->listen_path : (fwd->listen_host == NULL) ? (options.fwd_opts.gateway_ports ? "*" : "LOCALHOST") : fwd->listen_host, fwd->listen_port, (fwd->connect_path != NULL) ? fwd->connect_path : fwd->connect_host, fwd->connect_port); break; case MUX_FWD_DYNAMIC: xasprintf(&ret, "dynamic forward %.200s:%d -> *", (fwd->listen_host == NULL) ? (options.fwd_opts.gateway_ports ? "*" : "LOCALHOST") : fwd->listen_host, fwd->listen_port); break; case MUX_FWD_REMOTE: xasprintf(&ret, "remote forward %.200s:%d -> %.200s:%d", (fwd->listen_path != NULL) ? fwd->listen_path : (fwd->listen_host == NULL) ? "LOCALHOST" : fwd->listen_host, fwd->listen_port, (fwd->connect_path != NULL) ? fwd->connect_path : fwd->connect_host, fwd->connect_port); break; default: fatal_f("unknown forward type %u", ftype); } return ret; } static int compare_host(const char *a, const char *b) { if (a == NULL && b == NULL) return 1; if (a == NULL || b == NULL) return 0; return strcmp(a, b) == 0; } static int compare_forward(struct Forward *a, struct Forward *b) { if (!compare_host(a->listen_host, b->listen_host)) return 0; if (!compare_host(a->listen_path, b->listen_path)) return 0; if (a->listen_port != b->listen_port) return 0; if (!compare_host(a->connect_host, b->connect_host)) return 0; if (!compare_host(a->connect_path, b->connect_path)) return 0; if (a->connect_port != b->connect_port) return 0; return 1; } static void mux_confirm_remote_forward(struct ssh *ssh, int type, u_int32_t seq, void *ctxt) { struct mux_channel_confirm_ctx *fctx = ctxt; char *failmsg = NULL; struct Forward *rfwd; Channel *c; struct sshbuf *out; u_int port; int r; if ((c = channel_by_id(ssh, fctx->cid)) == NULL) { /* no channel for reply */ error_f("unknown channel"); return; } if ((out = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if (fctx->fid >= options.num_remote_forwards || (options.remote_forwards[fctx->fid].connect_path == NULL && options.remote_forwards[fctx->fid].connect_host == NULL)) { xasprintf(&failmsg, "unknown forwarding id %d", fctx->fid); goto fail; } rfwd = &options.remote_forwards[fctx->fid]; debug_f("%s for: listen %d, connect %s:%d", type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure", rfwd->listen_port, rfwd->connect_path ? rfwd->connect_path : rfwd->connect_host, rfwd->connect_port); if (type == SSH2_MSG_REQUEST_SUCCESS) { if (rfwd->listen_port == 0) { if ((r = sshpkt_get_u32(ssh, &port)) != 0) fatal_fr(r, "parse port"); if (port > 65535) { fatal("Invalid allocated port %u for " "mux remote forward to %s:%d", port, rfwd->connect_host, rfwd->connect_port); } rfwd->allocated_port = (int)port; debug("Allocated port %u for mux remote forward" " to %s:%d", rfwd->allocated_port, rfwd->connect_host, rfwd->connect_port); if ((r = sshbuf_put_u32(out, MUX_S_REMOTE_PORT)) != 0 || (r = sshbuf_put_u32(out, fctx->rid)) != 0 || (r = sshbuf_put_u32(out, rfwd->allocated_port)) != 0) fatal_fr(r, "reply"); channel_update_permission(ssh, rfwd->handle, rfwd->allocated_port); } else { reply_ok(out, fctx->rid); } goto out; } else { if (rfwd->listen_port == 0) channel_update_permission(ssh, rfwd->handle, -1); if (rfwd->listen_path != NULL) xasprintf(&failmsg, "remote port forwarding failed for " "listen path %s", rfwd->listen_path); else xasprintf(&failmsg, "remote port forwarding failed for " "listen port %d", rfwd->listen_port); debug2_f("clearing registered forwarding for listen %d, " "connect %s:%d", rfwd->listen_port, rfwd->connect_path ? rfwd->connect_path : rfwd->connect_host, rfwd->connect_port); free(rfwd->listen_host); free(rfwd->listen_path); free(rfwd->connect_host); free(rfwd->connect_path); memset(rfwd, 0, sizeof(*rfwd)); } fail: error_f("%s", failmsg); reply_error(out, MUX_S_FAILURE, fctx->rid, failmsg); free(failmsg); out: if ((r = sshbuf_put_stringb(c->output, out)) != 0) fatal_fr(r, "enqueue"); sshbuf_free(out); if (c->mux_pause <= 0) fatal_f("mux_pause %d", c->mux_pause); c->mux_pause = 0; /* start processing messages again */ } static int mux_master_process_open_fwd(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { struct Forward fwd; char *fwd_desc = NULL; char *listen_addr, *connect_addr; u_int ftype; u_int lport, cport; int r, i, ret = 0, freefwd = 1; memset(&fwd, 0, sizeof(fwd)); /* XXX - lport/cport check redundant */ if ((r = sshbuf_get_u32(m, &ftype)) != 0 || (r = sshbuf_get_cstring(m, &listen_addr, NULL)) != 0 || (r = sshbuf_get_u32(m, &lport)) != 0 || (r = sshbuf_get_cstring(m, &connect_addr, NULL)) != 0 || (r = sshbuf_get_u32(m, &cport)) != 0 || (lport != (u_int)PORT_STREAMLOCAL && lport > 65535) || (cport != (u_int)PORT_STREAMLOCAL && cport > 65535)) { error_f("malformed message"); ret = -1; goto out; } if (*listen_addr == '\0') { free(listen_addr); listen_addr = NULL; } if (*connect_addr == '\0') { free(connect_addr); connect_addr = NULL; } memset(&fwd, 0, sizeof(fwd)); fwd.listen_port = lport; if (fwd.listen_port == PORT_STREAMLOCAL) fwd.listen_path = listen_addr; else fwd.listen_host = listen_addr; fwd.connect_port = cport; if (fwd.connect_port == PORT_STREAMLOCAL) fwd.connect_path = connect_addr; else fwd.connect_host = connect_addr; debug2_f("channel %d: request %s", c->self, (fwd_desc = format_forward(ftype, &fwd))); if (ftype != MUX_FWD_LOCAL && ftype != MUX_FWD_REMOTE && ftype != MUX_FWD_DYNAMIC) { logit_f("invalid forwarding type %u", ftype); invalid: free(listen_addr); free(connect_addr); reply_error(reply, MUX_S_FAILURE, rid, "Invalid forwarding request"); return 0; } if (ftype == MUX_FWD_DYNAMIC && fwd.listen_path) { logit_f("streamlocal and dynamic forwards " "are mutually exclusive"); goto invalid; } if (fwd.listen_port != PORT_STREAMLOCAL && fwd.listen_port >= 65536) { logit_f("invalid listen port %u", fwd.listen_port); goto invalid; } if ((fwd.connect_port != PORT_STREAMLOCAL && fwd.connect_port >= 65536) || (ftype != MUX_FWD_DYNAMIC && ftype != MUX_FWD_REMOTE && fwd.connect_port == 0)) { logit_f("invalid connect port %u", fwd.connect_port); goto invalid; } if (ftype != MUX_FWD_DYNAMIC && fwd.connect_host == NULL && fwd.connect_path == NULL) { logit_f("missing connect host"); goto invalid; } /* Skip forwards that have already been requested */ switch (ftype) { case MUX_FWD_LOCAL: case MUX_FWD_DYNAMIC: for (i = 0; i < options.num_local_forwards; i++) { if (compare_forward(&fwd, options.local_forwards + i)) { exists: debug2_f("found existing forwarding"); reply_ok(reply, rid); goto out; } } break; case MUX_FWD_REMOTE: for (i = 0; i < options.num_remote_forwards; i++) { if (!compare_forward(&fwd, options.remote_forwards + i)) continue; if (fwd.listen_port != 0) goto exists; debug2_f("found allocated port"); if ((r = sshbuf_put_u32(reply, MUX_S_REMOTE_PORT)) != 0 || (r = sshbuf_put_u32(reply, rid)) != 0 || (r = sshbuf_put_u32(reply, options.remote_forwards[i].allocated_port)) != 0) fatal_fr(r, "reply FWD_REMOTE"); goto out; } break; } if (options.control_master == SSHCTL_MASTER_ASK || options.control_master == SSHCTL_MASTER_AUTO_ASK) { if (!ask_permission("Open %s on %s?", fwd_desc, host)) { debug2_f("forwarding refused by user"); reply_error(reply, MUX_S_PERMISSION_DENIED, rid, "Permission denied"); goto out; } } if (ftype == MUX_FWD_LOCAL || ftype == MUX_FWD_DYNAMIC) { if (!channel_setup_local_fwd_listener(ssh, &fwd, &options.fwd_opts)) { fail: logit_f("requested %s failed", fwd_desc); reply_error(reply, MUX_S_FAILURE, rid, "Port forwarding failed"); goto out; } add_local_forward(&options, &fwd); freefwd = 0; } else { struct mux_channel_confirm_ctx *fctx; fwd.handle = channel_request_remote_forwarding(ssh, &fwd); if (fwd.handle < 0) goto fail; add_remote_forward(&options, &fwd); fctx = xcalloc(1, sizeof(*fctx)); fctx->cid = c->self; fctx->rid = rid; fctx->fid = options.num_remote_forwards - 1; client_register_global_confirm(mux_confirm_remote_forward, fctx); freefwd = 0; c->mux_pause = 1; /* wait for mux_confirm_remote_forward */ /* delayed reply in mux_confirm_remote_forward */ goto out; } reply_ok(reply, rid); out: free(fwd_desc); if (freefwd) { free(fwd.listen_host); free(fwd.listen_path); free(fwd.connect_host); free(fwd.connect_path); } return ret; } static int mux_master_process_close_fwd(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { struct Forward fwd, *found_fwd; char *fwd_desc = NULL; const char *error_reason = NULL; char *listen_addr = NULL, *connect_addr = NULL; u_int ftype; int r, i, ret = 0; u_int lport, cport; memset(&fwd, 0, sizeof(fwd)); if ((r = sshbuf_get_u32(m, &ftype)) != 0 || (r = sshbuf_get_cstring(m, &listen_addr, NULL)) != 0 || (r = sshbuf_get_u32(m, &lport)) != 0 || (r = sshbuf_get_cstring(m, &connect_addr, NULL)) != 0 || (r = sshbuf_get_u32(m, &cport)) != 0 || (lport != (u_int)PORT_STREAMLOCAL && lport > 65535) || (cport != (u_int)PORT_STREAMLOCAL && cport > 65535)) { error_f("malformed message"); ret = -1; goto out; } if (*listen_addr == '\0') { free(listen_addr); listen_addr = NULL; } if (*connect_addr == '\0') { free(connect_addr); connect_addr = NULL; } memset(&fwd, 0, sizeof(fwd)); fwd.listen_port = lport; if (fwd.listen_port == PORT_STREAMLOCAL) fwd.listen_path = listen_addr; else fwd.listen_host = listen_addr; fwd.connect_port = cport; if (fwd.connect_port == PORT_STREAMLOCAL) fwd.connect_path = connect_addr; else fwd.connect_host = connect_addr; debug2_f("channel %d: request cancel %s", c->self, (fwd_desc = format_forward(ftype, &fwd))); /* make sure this has been requested */ found_fwd = NULL; switch (ftype) { case MUX_FWD_LOCAL: case MUX_FWD_DYNAMIC: for (i = 0; i < options.num_local_forwards; i++) { if (compare_forward(&fwd, options.local_forwards + i)) { found_fwd = options.local_forwards + i; break; } } break; case MUX_FWD_REMOTE: for (i = 0; i < options.num_remote_forwards; i++) { if (compare_forward(&fwd, options.remote_forwards + i)) { found_fwd = options.remote_forwards + i; break; } } break; } if (found_fwd == NULL) error_reason = "port not forwarded"; else if (ftype == MUX_FWD_REMOTE) { /* * This shouldn't fail unless we confused the host/port * between options.remote_forwards and permitted_opens. * However, for dynamic allocated listen ports we need * to use the actual listen port. */ if (channel_request_rforward_cancel(ssh, found_fwd) == -1) error_reason = "port not in permitted opens"; } else { /* local and dynamic forwards */ /* Ditto */ if (channel_cancel_lport_listener(ssh, &fwd, fwd.connect_port, &options.fwd_opts) == -1) error_reason = "port not found"; } if (error_reason != NULL) reply_error(reply, MUX_S_FAILURE, rid, error_reason); else { reply_ok(reply, rid); free(found_fwd->listen_host); free(found_fwd->listen_path); free(found_fwd->connect_host); free(found_fwd->connect_path); found_fwd->listen_host = found_fwd->connect_host = NULL; found_fwd->listen_path = found_fwd->connect_path = NULL; found_fwd->listen_port = found_fwd->connect_port = 0; } out: free(fwd_desc); free(listen_addr); free(connect_addr); return ret; } static int mux_master_process_stdio_fwd(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { Channel *nc; char *chost = NULL; u_int _cport, i, j; int ok = 0, cport, r, new_fd[2]; struct mux_stdio_confirm_ctx *cctx; if ((r = sshbuf_skip_string(m)) != 0 || /* reserved */ (r = sshbuf_get_cstring(m, &chost, NULL)) != 0 || (r = sshbuf_get_u32(m, &_cport)) != 0) { free(chost); error_f("malformed message"); return -1; } if (_cport == (u_int)PORT_STREAMLOCAL) cport = PORT_STREAMLOCAL; else if (_cport <= INT_MAX) cport = (int)_cport; else { free(chost); error_f("invalid port 0x%x", _cport); return -1; } debug2_f("channel %d: stdio fwd to %s:%d", c->self, chost, cport); /* Gather fds from client */ for(i = 0; i < 2; i++) { if ((new_fd[i] = mm_receive_fd(c->sock)) == -1) { error_f("failed to receive fd %d from client", i); for (j = 0; j < i; j++) close(new_fd[j]); free(chost); /* prepare reply */ reply_error(reply, MUX_S_FAILURE, rid, "did not receive file descriptors"); return -1; } } debug3_f("got fds stdin %d, stdout %d", new_fd[0], new_fd[1]); /* XXX support multiple child sessions in future */ if (c->have_remote_id) { debug2_f("session already open"); reply_error(reply, MUX_S_FAILURE, rid, "Multiple sessions not supported"); cleanup: close(new_fd[0]); close(new_fd[1]); free(chost); return 0; } if (options.control_master == SSHCTL_MASTER_ASK || options.control_master == SSHCTL_MASTER_AUTO_ASK) { if (cport == PORT_STREAMLOCAL) { ok = ask_permission("Allow forward to path %s", chost); } else { ok = ask_permission("Allow forward to [%s]:%d? ", chost, cport); } if (!ok) { debug2_f("stdio fwd refused by user"); reply_error(reply, MUX_S_PERMISSION_DENIED, rid, "Permission denied"); goto cleanup; } } nc = channel_connect_stdio_fwd(ssh, chost, cport, new_fd[0], new_fd[1], CHANNEL_NONBLOCK_STDIO); free(chost); nc->ctl_chan = c->self; /* link session -> control channel */ c->remote_id = nc->self; /* link control -> session channel */ c->have_remote_id = 1; debug2_f("channel_new: %d control %d", nc->self, nc->ctl_chan); channel_register_cleanup(ssh, nc->self, mux_master_session_cleanup_cb, 1); cctx = xcalloc(1, sizeof(*cctx)); cctx->rid = rid; channel_register_open_confirm(ssh, nc->self, mux_stdio_confirm, cctx); c->mux_pause = 1; /* stop handling messages until open_confirm done */ /* reply is deferred, sent by mux_session_confirm */ return 0; } /* Callback on open confirmation in mux master for a mux stdio fwd session. */ static void mux_stdio_confirm(struct ssh *ssh, int id, int success, void *arg) { struct mux_stdio_confirm_ctx *cctx = arg; Channel *c, *cc; struct sshbuf *reply; int r; if (cctx == NULL) fatal_f("cctx == NULL"); if ((c = channel_by_id(ssh, id)) == NULL) fatal_f("no channel for id %d", id); if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL) fatal_f("channel %d lacks control channel %d", id, c->ctl_chan); if ((reply = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if (!success) { debug3_f("sending failure reply"); reply_error(reply, MUX_S_FAILURE, cctx->rid, "Session open refused by peer"); /* prepare reply */ goto done; } debug3_f("sending success reply"); /* prepare reply */ if ((r = sshbuf_put_u32(reply, MUX_S_SESSION_OPENED)) != 0 || (r = sshbuf_put_u32(reply, cctx->rid)) != 0 || (r = sshbuf_put_u32(reply, c->self)) != 0) fatal_fr(r, "reply"); done: /* Send reply */ if ((r = sshbuf_put_stringb(cc->output, reply)) != 0) fatal_fr(r, "enqueue"); sshbuf_free(reply); if (cc->mux_pause <= 0) fatal_f("mux_pause %d", cc->mux_pause); cc->mux_pause = 0; /* start processing messages again */ c->open_confirm_ctx = NULL; free(cctx); } static int mux_master_process_stop_listening(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { debug_f("channel %d: stop listening", c->self); if (options.control_master == SSHCTL_MASTER_ASK || options.control_master == SSHCTL_MASTER_AUTO_ASK) { if (!ask_permission("Disable further multiplexing on shared " "connection to %s? ", host)) { debug2_f("stop listen refused by user"); reply_error(reply, MUX_S_PERMISSION_DENIED, rid, "Permission denied"); return 0; } } if (mux_listener_channel != NULL) { channel_free(ssh, mux_listener_channel); client_stop_mux(); free(options.control_path); options.control_path = NULL; mux_listener_channel = NULL; muxserver_sock = -1; } reply_ok(reply, rid); return 0; } static int mux_master_process_proxy(struct ssh *ssh, u_int rid, Channel *c, struct sshbuf *m, struct sshbuf *reply) { int r; debug_f("channel %d: proxy request", c->self); c->mux_rcb = channel_proxy_downstream; if ((r = sshbuf_put_u32(reply, MUX_S_PROXY)) != 0 || (r = sshbuf_put_u32(reply, rid)) != 0) fatal_fr(r, "reply"); return 0; } /* Channel callbacks fired on read/write from mux client fd */ static int mux_master_read_cb(struct ssh *ssh, Channel *c) { struct mux_master_state *state = (struct mux_master_state *)c->mux_ctx; struct sshbuf *in = NULL, *out = NULL; u_int type, rid, i; int r, ret = -1; if ((out = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); /* Setup ctx and */ if (c->mux_ctx == NULL) { state = xcalloc(1, sizeof(*state)); c->mux_ctx = state; channel_register_cleanup(ssh, c->self, mux_master_control_cleanup_cb, 0); /* Send hello */ if ((r = sshbuf_put_u32(out, MUX_MSG_HELLO)) != 0 || (r = sshbuf_put_u32(out, SSHMUX_VER)) != 0) fatal_fr(r, "reply"); /* no extensions */ if ((r = sshbuf_put_stringb(c->output, out)) != 0) fatal_fr(r, "enqueue"); debug3_f("channel %d: hello sent", c->self); ret = 0; goto out; } /* Channel code ensures that we receive whole packets */ if ((r = sshbuf_froms(c->input, &in)) != 0) { malf: error_f("malformed message"); goto out; } if ((r = sshbuf_get_u32(in, &type)) != 0) goto malf; debug3_f("channel %d packet type 0x%08x len %zu", c->self, type, sshbuf_len(in)); if (type == MUX_MSG_HELLO) rid = 0; else { if (!state->hello_rcvd) { error_f("expected MUX_MSG_HELLO(0x%08x), " "received 0x%08x", MUX_MSG_HELLO, type); goto out; } if ((r = sshbuf_get_u32(in, &rid)) != 0) goto malf; } for (i = 0; mux_master_handlers[i].handler != NULL; i++) { if (type == mux_master_handlers[i].type) { ret = mux_master_handlers[i].handler(ssh, rid, c, in, out); break; } } if (mux_master_handlers[i].handler == NULL) { error_f("unsupported mux message 0x%08x", type); reply_error(out, MUX_S_FAILURE, rid, "unsupported request"); ret = 0; } /* Enqueue reply packet */ if (sshbuf_len(out) != 0 && (r = sshbuf_put_stringb(c->output, out)) != 0) fatal_fr(r, "enqueue"); out: sshbuf_free(in); sshbuf_free(out); return ret; } void mux_exit_message(struct ssh *ssh, Channel *c, int exitval) { struct sshbuf *m; Channel *mux_chan; int r; debug3_f("channel %d: exit message, exitval %d", c->self, exitval); if ((mux_chan = channel_by_id(ssh, c->ctl_chan)) == NULL) fatal_f("channel %d missing mux %d", c->self, c->ctl_chan); /* Append exit message packet to control socket output queue */ if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_S_EXIT_MESSAGE)) != 0 || (r = sshbuf_put_u32(m, c->self)) != 0 || (r = sshbuf_put_u32(m, exitval)) != 0 || (r = sshbuf_put_stringb(mux_chan->output, m)) != 0) fatal_fr(r, "reply"); sshbuf_free(m); } void mux_tty_alloc_failed(struct ssh *ssh, Channel *c) { struct sshbuf *m; Channel *mux_chan; int r; debug3_f("channel %d: TTY alloc failed", c->self); if ((mux_chan = channel_by_id(ssh, c->ctl_chan)) == NULL) fatal_f("channel %d missing mux %d", c->self, c->ctl_chan); /* Append exit message packet to control socket output queue */ if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_S_TTY_ALLOC_FAIL)) != 0 || (r = sshbuf_put_u32(m, c->self)) != 0 || (r = sshbuf_put_stringb(mux_chan->output, m)) != 0) fatal_fr(r, "reply"); sshbuf_free(m); } /* Prepare a mux master to listen on a Unix domain socket. */ void muxserver_listen(struct ssh *ssh) { mode_t old_umask; char *orig_control_path = options.control_path; char rbuf[16+1]; u_int i, r; int oerrno; if (options.control_path == NULL || options.control_master == SSHCTL_MASTER_NO) return; debug("setting up multiplex master socket"); /* * Use a temporary path before listen so we can pseudo-atomically * establish the listening socket in its final location to avoid * other processes racing in between bind() and listen() and hitting * an unready socket. */ for (i = 0; i < sizeof(rbuf) - 1; i++) { r = arc4random_uniform(26+26+10); rbuf[i] = (r < 26) ? 'a' + r : (r < 26*2) ? 'A' + r - 26 : '0' + r - 26 - 26; } rbuf[sizeof(rbuf) - 1] = '\0'; options.control_path = NULL; xasprintf(&options.control_path, "%s.%s", orig_control_path, rbuf); debug3_f("temporary control path %s", options.control_path); old_umask = umask(0177); muxserver_sock = unix_listener(options.control_path, 64, 0); oerrno = errno; umask(old_umask); if (muxserver_sock < 0) { if (oerrno == EINVAL || oerrno == EADDRINUSE) { error("ControlSocket %s already exists, " "disabling multiplexing", options.control_path); disable_mux_master: if (muxserver_sock != -1) { close(muxserver_sock); muxserver_sock = -1; } free(orig_control_path); free(options.control_path); options.control_path = NULL; options.control_master = SSHCTL_MASTER_NO; return; } else { /* unix_listener() logs the error */ cleanup_exit(254); } } /* Now atomically "move" the mux socket into position */ if (link(options.control_path, orig_control_path) != 0) { if (errno != EEXIST) { fatal_f("link mux listener %s => %s: %s", options.control_path, orig_control_path, strerror(errno)); } error("ControlSocket %s already exists, disabling multiplexing", orig_control_path); unlink(options.control_path); goto disable_mux_master; } unlink(options.control_path); free(options.control_path); options.control_path = orig_control_path; set_nonblock(muxserver_sock); mux_listener_channel = channel_new(ssh, "mux listener", SSH_CHANNEL_MUX_LISTENER, muxserver_sock, muxserver_sock, -1, CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, options.control_path, 1); mux_listener_channel->mux_rcb = mux_master_read_cb; debug3_f("mux listener channel %d fd %d", mux_listener_channel->self, mux_listener_channel->sock); } /* Callback on open confirmation in mux master for a mux client session. */ static void mux_session_confirm(struct ssh *ssh, int id, int success, void *arg) { struct mux_session_confirm_ctx *cctx = arg; const char *display; Channel *c, *cc; int i, r; struct sshbuf *reply; if (cctx == NULL) fatal_f("cctx == NULL"); if ((c = channel_by_id(ssh, id)) == NULL) fatal_f("no channel for id %d", id); if ((cc = channel_by_id(ssh, c->ctl_chan)) == NULL) fatal_f("channel %d lacks control channel %d", id, c->ctl_chan); if ((reply = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if (!success) { debug3_f("sending failure reply"); reply_error(reply, MUX_S_FAILURE, cctx->rid, "Session open refused by peer"); goto done; } display = getenv("DISPLAY"); if (cctx->want_x_fwd && options.forward_x11 && display != NULL) { char *proto, *data; /* Get reasonable local authentication information. */ if (client_x11_get_proto(ssh, display, options.xauth_location, options.forward_x11_trusted, options.forward_x11_timeout, &proto, &data) == 0) { /* Request forwarding with authentication spoofing. */ debug("Requesting X11 forwarding with authentication " "spoofing."); x11_request_forwarding_with_spoofing(ssh, id, display, proto, data, 1); /* XXX exit_on_forward_failure */ client_expect_confirm(ssh, id, "X11 forwarding", CONFIRM_WARN); } } if (cctx->want_agent_fwd && options.forward_agent) { debug("Requesting authentication agent forwarding."); channel_request_start(ssh, id, "auth-agent-req@openssh.com", 0); if ((r = sshpkt_send(ssh)) != 0) fatal_fr(r, "send"); } client_session2_setup(ssh, id, cctx->want_tty, cctx->want_subsys, cctx->term, &cctx->tio, c->rfd, cctx->cmd, cctx->env); debug3_f("sending success reply"); /* prepare reply */ if ((r = sshbuf_put_u32(reply, MUX_S_SESSION_OPENED)) != 0 || (r = sshbuf_put_u32(reply, cctx->rid)) != 0 || (r = sshbuf_put_u32(reply, c->self)) != 0) fatal_fr(r, "reply"); done: /* Send reply */ if ((r = sshbuf_put_stringb(cc->output, reply)) != 0) fatal_fr(r, "enqueue"); sshbuf_free(reply); if (cc->mux_pause <= 0) fatal_f("mux_pause %d", cc->mux_pause); cc->mux_pause = 0; /* start processing messages again */ c->open_confirm_ctx = NULL; sshbuf_free(cctx->cmd); free(cctx->term); if (cctx->env != NULL) { for (i = 0; cctx->env[i] != NULL; i++) free(cctx->env[i]); free(cctx->env); } free(cctx); } /* ** Multiplexing client support */ /* Exit signal handler */ static void control_client_sighandler(int signo) { muxclient_terminate = signo; } /* * Relay signal handler - used to pass some signals from mux client to * mux master. */ static void control_client_sigrelay(int signo) { int save_errno = errno; if (muxserver_pid > 1) kill(muxserver_pid, signo); errno = save_errno; } static int mux_client_read(int fd, struct sshbuf *b, size_t need, int timeout_ms) { size_t have; ssize_t len; u_char *p; int r; if ((r = sshbuf_reserve(b, need, &p)) != 0) fatal_fr(r, "reserve"); for (have = 0; have < need; ) { if (muxclient_terminate) { errno = EINTR; return -1; } len = read(fd, p + have, need - have); if (len == -1) { switch (errno) { case EAGAIN: if (waitrfd(fd, &timeout_ms, &muxclient_terminate) == -1 && errno != EINTR) return -1; /* timeout */ /* FALLTHROUGH */ case EINTR: continue; default: return -1; } } if (len == 0) { errno = EPIPE; return -1; } have += (size_t)len; } return 0; } static int mux_client_write_packet(int fd, struct sshbuf *m) { struct sshbuf *queue; u_int have, need; int r, oerrno, len; const u_char *ptr; struct pollfd pfd; pfd.fd = fd; pfd.events = POLLOUT; if ((queue = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_stringb(queue, m)) != 0) fatal_fr(r, "enqueue"); need = sshbuf_len(queue); ptr = sshbuf_ptr(queue); for (have = 0; have < need; ) { if (muxclient_terminate) { sshbuf_free(queue); errno = EINTR; return -1; } len = write(fd, ptr + have, need - have); if (len == -1) { switch (errno) { case EAGAIN: (void)poll(&pfd, 1, -1); /* FALLTHROUGH */ case EINTR: continue; default: oerrno = errno; sshbuf_free(queue); errno = oerrno; return -1; } } if (len == 0) { sshbuf_free(queue); errno = EPIPE; return -1; } have += (u_int)len; } sshbuf_free(queue); return 0; } static int mux_client_read_packet_timeout(int fd, struct sshbuf *m, int timeout_ms) { struct sshbuf *queue; size_t need, have; const u_char *ptr; int r, oerrno; if ((queue = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if (mux_client_read(fd, queue, 4, timeout_ms) != 0) { if ((oerrno = errno) == EPIPE) debug3_f("read header failed: %s", strerror(errno)); sshbuf_free(queue); errno = oerrno; return -1; } need = PEEK_U32(sshbuf_ptr(queue)); if (mux_client_read(fd, queue, need, timeout_ms) != 0) { oerrno = errno; debug3_f("read body failed: %s", strerror(errno)); sshbuf_free(queue); errno = oerrno; return -1; } if ((r = sshbuf_get_string_direct(queue, &ptr, &have)) != 0 || (r = sshbuf_put(m, ptr, have)) != 0) fatal_fr(r, "dequeue"); sshbuf_free(queue); return 0; } static int mux_client_read_packet(int fd, struct sshbuf *m) { return mux_client_read_packet_timeout(fd, m, -1); } static int mux_client_hello_exchange(int fd, int timeout_ms) { struct sshbuf *m; u_int type, ver; int r, ret = -1; if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_MSG_HELLO)) != 0 || (r = sshbuf_put_u32(m, SSHMUX_VER)) != 0) fatal_fr(r, "assemble hello"); /* no extensions */ if (mux_client_write_packet(fd, m) != 0) { debug_f("write packet: %s", strerror(errno)); goto out; } sshbuf_reset(m); /* Read their HELLO */ if (mux_client_read_packet_timeout(fd, m, timeout_ms) != 0) { debug_f("read packet failed"); goto out; } if ((r = sshbuf_get_u32(m, &type)) != 0) fatal_fr(r, "parse type"); if (type != MUX_MSG_HELLO) { error_f("expected HELLO (%u) got %u", MUX_MSG_HELLO, type); goto out; } if ((r = sshbuf_get_u32(m, &ver)) != 0) fatal_fr(r, "parse version"); if (ver != SSHMUX_VER) { error("Unsupported multiplexing protocol version %d " "(expected %d)", ver, SSHMUX_VER); goto out; } debug2_f("master version %u", ver); /* No extensions are presently defined */ while (sshbuf_len(m) > 0) { char *name = NULL; if ((r = sshbuf_get_cstring(m, &name, NULL)) != 0 || (r = sshbuf_skip_string(m)) != 0) { /* value */ error_fr(r, "parse extension"); goto out; } debug2("Unrecognised master extension \"%s\"", name); free(name); } /* success */ ret = 0; out: sshbuf_free(m); return ret; } static u_int mux_client_request_alive(int fd) { struct sshbuf *m; char *e; u_int pid, type, rid; int r; debug3_f("entering"); if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_ALIVE_CHECK)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0) fatal_fr(r, "assemble"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); sshbuf_reset(m); /* Read their reply */ if (mux_client_read_packet(fd, m) != 0) { sshbuf_free(m); return 0; } if ((r = sshbuf_get_u32(m, &type)) != 0) fatal_fr(r, "parse type"); if (type != MUX_S_ALIVE) { if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal_f("master returned error: %s", e); } if ((r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse remote ID"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); if ((r = sshbuf_get_u32(m, &pid)) != 0) fatal_fr(r, "parse PID"); sshbuf_free(m); debug3_f("done pid = %u", pid); muxclient_request_id++; return pid; } static void mux_client_request_terminate(int fd) { struct sshbuf *m; char *e; u_int type, rid; int r; debug3_f("entering"); if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_TERMINATE)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0) fatal_fr(r, "request"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); sshbuf_reset(m); /* Read their reply */ if (mux_client_read_packet(fd, m) != 0) { /* Remote end exited already */ if (errno == EPIPE) { sshbuf_free(m); return; } fatal_f("read from master failed: %s", strerror(errno)); } if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); switch (type) { case MUX_S_OK: break; case MUX_S_PERMISSION_DENIED: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal("Master refused termination request: %s", e); case MUX_S_FAILURE: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal_f("termination request failed: %s", e); default: fatal_f("unexpected response from master 0x%08x", type); } sshbuf_free(m); muxclient_request_id++; } static int mux_client_forward(int fd, int cancel_flag, u_int ftype, struct Forward *fwd) { struct sshbuf *m; char *e, *fwd_desc; const char *lhost, *chost; u_int type, rid; int r; fwd_desc = format_forward(ftype, fwd); debug("Requesting %s %s", cancel_flag ? "cancellation of" : "forwarding of", fwd_desc); free(fwd_desc); type = cancel_flag ? MUX_C_CLOSE_FWD : MUX_C_OPEN_FWD; if (fwd->listen_path != NULL) lhost = fwd->listen_path; else if (fwd->listen_host == NULL) lhost = ""; else if (*fwd->listen_host == '\0') lhost = "*"; else lhost = fwd->listen_host; if (fwd->connect_path != NULL) chost = fwd->connect_path; else if (fwd->connect_host == NULL) chost = ""; else chost = fwd->connect_host; if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, type)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 || (r = sshbuf_put_u32(m, ftype)) != 0 || (r = sshbuf_put_cstring(m, lhost)) != 0 || (r = sshbuf_put_u32(m, fwd->listen_port)) != 0 || (r = sshbuf_put_cstring(m, chost)) != 0 || (r = sshbuf_put_u32(m, fwd->connect_port)) != 0) fatal_fr(r, "request"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); sshbuf_reset(m); /* Read their reply */ if (mux_client_read_packet(fd, m) != 0) { sshbuf_free(m); return -1; } if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); switch (type) { case MUX_S_OK: break; case MUX_S_REMOTE_PORT: if (cancel_flag) fatal_f("got MUX_S_REMOTE_PORT for cancel"); if ((r = sshbuf_get_u32(m, &fwd->allocated_port)) != 0) fatal_fr(r, "parse port"); verbose("Allocated port %u for remote forward to %s:%d", fwd->allocated_port, fwd->connect_host ? fwd->connect_host : "", fwd->connect_port); if (muxclient_command == SSHMUX_COMMAND_FORWARD) fprintf(stdout, "%i\n", fwd->allocated_port); break; case MUX_S_PERMISSION_DENIED: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); sshbuf_free(m); error("Master refused forwarding request: %s", e); return -1; case MUX_S_FAILURE: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); sshbuf_free(m); error_f("forwarding request failed: %s", e); return -1; default: fatal_f("unexpected response from master 0x%08x", type); } sshbuf_free(m); muxclient_request_id++; return 0; } static int mux_client_forwards(int fd, int cancel_flag) { int i, ret = 0; debug3_f("%s forwardings: %d local, %d remote", cancel_flag ? "cancel" : "request", options.num_local_forwards, options.num_remote_forwards); /* XXX ExitOnForwardingFailure */ for (i = 0; i < options.num_local_forwards; i++) { if (mux_client_forward(fd, cancel_flag, options.local_forwards[i].connect_port == 0 ? MUX_FWD_DYNAMIC : MUX_FWD_LOCAL, options.local_forwards + i) != 0) ret = -1; } for (i = 0; i < options.num_remote_forwards; i++) { if (mux_client_forward(fd, cancel_flag, MUX_FWD_REMOTE, options.remote_forwards + i) != 0) ret = -1; } return ret; } static int mux_client_request_session(int fd) { struct sshbuf *m; char *e; const char *term = NULL; u_int i, echar, rid, sid, esid, exitval, type, exitval_seen; extern char **environ; int r, rawmode = 0; debug3_f("entering"); if ((muxserver_pid = mux_client_request_alive(fd)) == 0) { error_f("master alive request failed"); return -1; } ssh_signal(SIGPIPE, SIG_IGN); if (options.stdin_null && stdfd_devnull(1, 0, 0) == -1) fatal_f("stdfd_devnull failed"); if ((term = lookup_env_in_list("TERM", options.setenv, options.num_setenv)) == NULL || *term == '\0') term = getenv("TERM"); echar = 0xffffffff; if (options.escape_char != SSH_ESCAPECHAR_NONE) echar = (u_int)options.escape_char; if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_NEW_SESSION)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 || (r = sshbuf_put_string(m, NULL, 0)) != 0 || /* reserved */ (r = sshbuf_put_u32(m, tty_flag)) != 0 || (r = sshbuf_put_u32(m, options.forward_x11)) != 0 || (r = sshbuf_put_u32(m, options.forward_agent)) != 0 || (r = sshbuf_put_u32(m, options.session_type == SESSION_TYPE_SUBSYSTEM)) != 0 || (r = sshbuf_put_u32(m, echar)) != 0 || (r = sshbuf_put_cstring(m, term == NULL ? "" : term)) != 0 || (r = sshbuf_put_stringb(m, command)) != 0) fatal_fr(r, "request"); /* Pass environment */ if (options.num_send_env > 0 && environ != NULL) { for (i = 0; environ[i] != NULL; i++) { if (!env_permitted(environ[i])) continue; if ((r = sshbuf_put_cstring(m, environ[i])) != 0) fatal_fr(r, "request sendenv"); } } for (i = 0; i < options.num_setenv; i++) { if ((r = sshbuf_put_cstring(m, options.setenv[i])) != 0) fatal_fr(r, "request setenv"); } if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); /* Send the stdio file descriptors */ if (mm_send_fd(fd, STDIN_FILENO) == -1 || mm_send_fd(fd, STDOUT_FILENO) == -1 || mm_send_fd(fd, STDERR_FILENO) == -1) fatal_f("send fds failed"); debug3_f("session request sent"); /* Read their reply */ sshbuf_reset(m); if (mux_client_read_packet(fd, m) != 0) { error_f("read from master failed: %s", strerror(errno)); sshbuf_free(m); return -1; } if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); switch (type) { case MUX_S_SESSION_OPENED: if ((r = sshbuf_get_u32(m, &sid)) != 0) fatal_fr(r, "parse session ID"); debug_f("master session id: %u", sid); break; case MUX_S_PERMISSION_DENIED: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); error("Master refused session request: %s", e); sshbuf_free(m); return -1; case MUX_S_FAILURE: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); error_f("session request failed: %s", e); sshbuf_free(m); return -1; default: sshbuf_free(m); error_f("unexpected response from master 0x%08x", type); return -1; } muxclient_request_id++; #ifdef __OpenBSD__ if (pledge("stdio proc tty", NULL) == -1) fatal_f("pledge(): %s", strerror(errno)); #endif ssh_signal(SIGHUP, control_client_sighandler); ssh_signal(SIGINT, control_client_sighandler); ssh_signal(SIGTERM, control_client_sighandler); ssh_signal(SIGWINCH, control_client_sigrelay); if (options.fork_after_authentication) daemon(1, 1); else { rawmode = tty_flag; if (tty_flag) { enter_raw_mode( options.request_tty == REQUEST_TTY_FORCE); } } /* * Stick around until the controlee closes the client_fd. * Before it does, it is expected to write an exit message. * This process must read the value and wait for the closure of * the client_fd; if this one closes early, the multiplex master will * terminate early too (possibly losing data). */ for (exitval = 255, exitval_seen = 0;;) { sshbuf_reset(m); if (mux_client_read_packet(fd, m) != 0) break; if ((r = sshbuf_get_u32(m, &type)) != 0) fatal_fr(r, "parse type"); switch (type) { case MUX_S_TTY_ALLOC_FAIL: if ((r = sshbuf_get_u32(m, &esid)) != 0) fatal_fr(r, "parse session ID"); if (esid != sid) fatal_f("tty alloc fail on unknown session: " "my id %u theirs %u", sid, esid); leave_raw_mode(options.request_tty == REQUEST_TTY_FORCE); rawmode = 0; continue; case MUX_S_EXIT_MESSAGE: if ((r = sshbuf_get_u32(m, &esid)) != 0) fatal_fr(r, "parse session ID"); if (esid != sid) fatal_f("exit on unknown session: " "my id %u theirs %u", sid, esid); if (exitval_seen) fatal_f("exitval sent twice"); if ((r = sshbuf_get_u32(m, &exitval)) != 0) fatal_fr(r, "parse exitval"); exitval_seen = 1; continue; default: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal_f("master returned error: %s", e); } } close(fd); if (rawmode) leave_raw_mode(options.request_tty == REQUEST_TTY_FORCE); if (muxclient_terminate) { debug2("Exiting on signal: %s", strsignal(muxclient_terminate)); exitval = 255; } else if (!exitval_seen) { debug2("Control master terminated unexpectedly"); exitval = 255; } else debug2("Received exit status from master %d", exitval); if (tty_flag && options.log_level >= SYSLOG_LEVEL_INFO) fprintf(stderr, "Shared connection to %s closed.\r\n", host); exit(exitval); } static int mux_client_proxy(int fd) { struct sshbuf *m; char *e; u_int type, rid; int r; if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_PROXY)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0) fatal_fr(r, "request"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); sshbuf_reset(m); /* Read their reply */ if (mux_client_read_packet(fd, m) != 0) { sshbuf_free(m); return 0; } if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); if (type != MUX_S_PROXY) { if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal_f("master returned error: %s", e); } sshbuf_free(m); debug3_f("done"); muxclient_request_id++; return 0; } static int mux_client_request_stdio_fwd(int fd) { struct sshbuf *m; char *e; u_int type, rid, sid; int r; debug3_f("entering"); if ((muxserver_pid = mux_client_request_alive(fd)) == 0) { error_f("master alive request failed"); return -1; } ssh_signal(SIGPIPE, SIG_IGN); if (options.stdin_null && stdfd_devnull(1, 0, 0) == -1) fatal_f("stdfd_devnull failed"); if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_NEW_STDIO_FWD)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0 || (r = sshbuf_put_string(m, NULL, 0)) != 0 || /* reserved */ (r = sshbuf_put_cstring(m, options.stdio_forward_host)) != 0 || (r = sshbuf_put_u32(m, options.stdio_forward_port)) != 0) fatal_fr(r, "request"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); /* Send the stdio file descriptors */ if (mm_send_fd(fd, STDIN_FILENO) == -1 || mm_send_fd(fd, STDOUT_FILENO) == -1) fatal_f("send fds failed"); #ifdef __OpenBSD__ if (pledge("stdio proc tty", NULL) == -1) fatal_f("pledge(): %s", strerror(errno)); #endif debug3_f("stdio forward request sent"); /* Read their reply */ sshbuf_reset(m); if (mux_client_read_packet(fd, m) != 0) { error_f("read from master failed: %s", strerror(errno)); sshbuf_free(m); return -1; } if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); switch (type) { case MUX_S_SESSION_OPENED: if ((r = sshbuf_get_u32(m, &sid)) != 0) fatal_fr(r, "parse session ID"); debug_f("master session id: %u", sid); break; case MUX_S_PERMISSION_DENIED: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); sshbuf_free(m); fatal("Master refused stdio forwarding request: %s", e); case MUX_S_FAILURE: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); sshbuf_free(m); fatal("Stdio forwarding request failed: %s", e); default: sshbuf_free(m); error_f("unexpected response from master 0x%08x", type); return -1; } muxclient_request_id++; ssh_signal(SIGHUP, control_client_sighandler); ssh_signal(SIGINT, control_client_sighandler); ssh_signal(SIGTERM, control_client_sighandler); ssh_signal(SIGWINCH, control_client_sigrelay); /* * Stick around until the controlee closes the client_fd. */ sshbuf_reset(m); if (mux_client_read_packet(fd, m) != 0) { if (errno == EPIPE || (errno == EINTR && muxclient_terminate != 0)) return 0; fatal_f("mux_client_read_packet: %s", strerror(errno)); } fatal_f("master returned unexpected message %u", type); } static void mux_client_request_stop_listening(int fd) { struct sshbuf *m; char *e; u_int type, rid; int r; debug3_f("entering"); if ((m = sshbuf_new()) == NULL) fatal_f("sshbuf_new"); if ((r = sshbuf_put_u32(m, MUX_C_STOP_LISTENING)) != 0 || (r = sshbuf_put_u32(m, muxclient_request_id)) != 0) fatal_fr(r, "request"); if (mux_client_write_packet(fd, m) != 0) fatal_f("write packet: %s", strerror(errno)); sshbuf_reset(m); /* Read their reply */ if (mux_client_read_packet(fd, m) != 0) fatal_f("read from master failed: %s", strerror(errno)); if ((r = sshbuf_get_u32(m, &type)) != 0 || (r = sshbuf_get_u32(m, &rid)) != 0) fatal_fr(r, "parse"); if (rid != muxclient_request_id) fatal_f("out of sequence reply: my id %u theirs %u", muxclient_request_id, rid); switch (type) { case MUX_S_OK: break; case MUX_S_PERMISSION_DENIED: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal("Master refused stop listening request: %s", e); case MUX_S_FAILURE: if ((r = sshbuf_get_cstring(m, &e, NULL)) != 0) fatal_fr(r, "parse error message"); fatal_f("stop listening request failed: %s", e); default: fatal_f("unexpected response from master 0x%08x", type); } sshbuf_free(m); muxclient_request_id++; } /* Multiplex client main loop. */ int muxclient(const char *path) { struct sockaddr_un addr; int sock, timeout = options.connection_timeout, timeout_ms = -1; u_int pid; if (muxclient_command == 0) { if (options.stdio_forward_host != NULL) muxclient_command = SSHMUX_COMMAND_STDIO_FWD; else muxclient_command = SSHMUX_COMMAND_OPEN; } switch (options.control_master) { case SSHCTL_MASTER_AUTO: case SSHCTL_MASTER_AUTO_ASK: debug("auto-mux: Trying existing master at '%s'", path); /* FALLTHROUGH */ case SSHCTL_MASTER_NO: break; default: return -1; } memset(&addr, '\0', sizeof(addr)); addr.sun_family = AF_UNIX; if (strlcpy(addr.sun_path, path, sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) fatal("ControlPath too long ('%s' >= %u bytes)", path, (unsigned int)sizeof(addr.sun_path)); if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) == -1) fatal_f("socket(): %s", strerror(errno)); if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1) { switch (muxclient_command) { case SSHMUX_COMMAND_OPEN: case SSHMUX_COMMAND_STDIO_FWD: break; default: fatal("Control socket connect(%.100s): %s", path, strerror(errno)); } if (errno == ECONNREFUSED && options.control_master != SSHCTL_MASTER_NO) { debug("Stale control socket %.100s, unlinking", path); unlink(path); } else if (errno == ENOENT) { debug("Control socket \"%.100s\" does not exist", path); } else { error("Control socket connect(%.100s): %s", path, strerror(errno)); } close(sock); return -1; } set_nonblock(sock); /* Timeout on initial connection only. */ if (timeout > 0 && timeout < INT_MAX / 1000) timeout_ms = timeout * 1000; if (mux_client_hello_exchange(sock, timeout_ms) != 0) { error_f("master hello exchange failed"); close(sock); return -1; } switch (muxclient_command) { case SSHMUX_COMMAND_ALIVE_CHECK: if ((pid = mux_client_request_alive(sock)) == 0) fatal_f("master alive check failed"); fprintf(stderr, "Master running (pid=%u)\r\n", pid); exit(0); case SSHMUX_COMMAND_TERMINATE: mux_client_request_terminate(sock); if (options.log_level != SYSLOG_LEVEL_QUIET) fprintf(stderr, "Exit request sent.\r\n"); exit(0); case SSHMUX_COMMAND_FORWARD: if (mux_client_forwards(sock, 0) != 0) fatal_f("master forward request failed"); exit(0); case SSHMUX_COMMAND_OPEN: if (mux_client_forwards(sock, 0) != 0) { error_f("master forward request failed"); return -1; } mux_client_request_session(sock); return -1; case SSHMUX_COMMAND_STDIO_FWD: mux_client_request_stdio_fwd(sock); exit(0); case SSHMUX_COMMAND_STOP: mux_client_request_stop_listening(sock); if (options.log_level != SYSLOG_LEVEL_QUIET) fprintf(stderr, "Stop listening request sent.\r\n"); exit(0); case SSHMUX_COMMAND_CANCEL_FWD: if (mux_client_forwards(sock, 1) != 0) error_f("master cancel forward request failed"); exit(0); case SSHMUX_COMMAND_PROXY: mux_client_proxy(sock); return (sock); default: fatal("unrecognised muxclient_command %d", muxclient_command); } }